diff --git a/tests/ui/cast_alignment.rs b/tests/ui/cast_alignment.rs
index efc56ea2bbc1..77f50b3add29 100644
--- a/tests/ui/cast_alignment.rs
+++ b/tests/ui/cast_alignment.rs
@@ -9,8 +9,8 @@
 
 //! Test casts for alignment issues
 
-#![feature(libc)]
 
+#![feature(rustc_private)]
 extern crate libc;
 
 #[warn(clippy::cast_ptr_alignment)]